1. Field of the Invention
This invention relates to liquid compositions which do not contribute to the VOC of paints and coatings, which are stable against decoloration and, particularly, are a mixture of 3-iodo-2-propynyl butyl carbamate (IPBC) and polyethylene glycol (PEG), or propylene glycol (PPG) or propylene glycol glyceryl esters (PGGE), or their combinations.
2. Description of the Prior Art
Various methods and compositions have been described to stabilize biocidal compositions containing IPBC, for example, using UV absorbers and/or organic epoxides in a liquid vehicle, as shown in U.S. Pat. Nos. 4,276,211; 4,552,885; 5,938,825; 6,059,991 and 6,140,370. Organic solvents such as N-methyl pyrrolidone (NMP), Texanol(copyright) ester alcohols, and dimethyl oxide (DMSO) are typical solvents for IPBC. Singer, W. et al, in U.S. Pat. No. 4,276,211, for example, described paint compositions containing iodoalkyne carbamates which were color stabilized by addition thereto of selected epoxy compounds. However, none of these references provide a stable IPBC composition which is also low in volatile organic compounds (VOC). In many jurisdictions, the local regulatory authority has established very low limits on the amount of VOC released upon use of the product. It is therefore desirable to minimize the VOC of additives in all materials sold for use in these jurisdictions.
Tanaka, Y. et al, in Japanese application No. Hei 11 (1999)-21205, described a vinyl chloride resin molding composition, where the antimicrobial and antifungal agent IPBC was first dissolved in a polyalkylene glycol plasticizer to facilitate the molding process and disperse the IPBC uniformly throughout the vinyl chloride resin before molding. The vinyl chloride resin molding composition did not discolor substantially when kneaded at a temperature above 200xc2x0 C. However, no paint and coating compositions were disclosed or suggested in this reference.
The use of biocides to protect paint formulations and coatings, is of great commercial importance. One biocide widely used in paint compositions is 3-iodo-2-propynyl butyl carbamate, also referred to as IPBC. Unfortunately, many biocidal compositions containing IPBC are susceptible to decomposition under conditions of high temperature and exposure to sunlight. The decomposition of IPBC typically results in the formation of a yellow or brown by-product and also reduces the efficacy of the additive.
Color instability can become evident when the compositions containing IPBC are stored for extended periods of time in a warehouse in warm climates or when exposed to sunlight. The color of such compositions will turn dark brown. The compositions thus will be unsuitable for use in certain systems in need of antimicrobial protection particularly white aqueous paints. Furthermore, decomposition of the IPBC can render the biocidal composition less effective in controlling microbial growth.
In addition to the tendency of IPBC compositions to darken in color upon storage, the incorporation of IPBC into various formulations can also produce yellowing of dried films upon exposure of the film to direct sunlight. Obviously, this discoloration is undesirable and limits the use of such IPBC compositions.
What is described herein is a liquid composition consisting essentially of by weight, 0.1-50% IPBC in 99.9-50% polyethylene glycol, polypropylene glycol or polypropylene glycol glyceryl, or mixtures thereof, which does not contribute to the VOC of paints and coatings, and is stabilized effectively against decoloration even at elevated temperatures or under direct sunlight.